Susanne Olsson

A Different Approach to Enantioselective Organic Synthesis: Absolute Asymmetric Synthesis of Organometallic Reagents†

Voilà, optical activity: Both enantiomers of 1-chloroindene have been synthesized in high selectivity from solely achiral starting materials, and without using optically active catalysts (see scheme). These symmetry-breaking syntheses provide a proof-of-concept for a new approach to asymmetric synthesis. NCS=N-chlorosuccinimide.

Absolute Asymmetric Synthesis: Protected Substrate Oxidation

Three new conglomerates incorporating bidentate sulfide ligands coordinated by Ru(II) centers have been prepared. Total spontaneous resolution by slow crystallization gives highly enantioenriched crystal batches, which are used in enantioselective oxidation of the sulfide ligands to give chiral sulfoxide complexes with >98 % ee. All relevant stereoisomers have been characterized by single-crystal X-ray diffraction, CD spectroscopy, and chiral HPLC. If the ligand range can be extended to monodentate sulfides, a large-scale and recyclable process for enantioselective oxidation of sulfides can be designed.

Absolute Asymmetric Synthesis of a Tetrahedral Silver Complex

Even though the isolation of tetrahedral stereoisomers usually presents a synthetic challenge, a highly enantioenriched tetrahedral silver complex could be easily accessed by either crystallization or Viedma ripening. The overall preparation may be regarded as an example of absolute asymmetric synthesis. Experimental results indicate that both crystallization and Viedma ripening follow a similar cluster-controlled mechanism.

catena-Poly[[[aqua­(propane-1,3-diamine-κ2N,N′)copper(II)]-μ-fumarato-κ2O:O′] monohydrate]

The asymmetric unit of the title compound, {[Cu(C4H2O4)(C3H10N2)(H2O)]·H2O}n, consists of two CuII atoms, half each of two propane-1,3-diamine ligands and two coordinated water molecules, all lying on crystallographic mirror planes, also one fumarate dianion and one uncoordinated water molecule in a general position. The Cu(C3H10N2)(H2O) units are linked via fumarate dianions into a zigzag chain running along the a axis. A longer Cu—O distance [2.873 (3) Å] is to a water molecule bridging equivalent CuII atoms in adjacent chains, forming a three-dimensional framework. One of the CuII atoms is in a distorted square-pyramidal environment and the other is in a pseudo-octahedral geometry of the [5+1] type. O—H⋯O and N—H⋯O hydrogen bonds are observed in the crystal structure.

[4-(2-Amino­ethyl)-1,4,7,10-tetra­azadeca­ne]lithium chloride: a bilayered structure displaying the rare TRENEN ligand

The pentadentate ligand TRENEN [4-(2-aminoetyl)-1,4,7,10-tetraazadecane] is not readily available in the pure state, but is present as a major impurity in commercial tetraethylene pentamine. Therefore, only four structures containing TRENEN have been reported previously. We report here the crystal structure of the title compound, [Li(trenen)]Cl or [Li(C8H23N5)]Cl. The Li atom has a distorted trigonal bipyramidal coordination geometry. The [Li(trenen)](+) cation is chiral since one of the N atoms is a chirogenic centre. A second type of chirality arises as a consequence of the chelatering conformations. In the racemic crystal structure, molecules assemble into bilayers via N - H center dot center dot center dot Cl interactions.